The Bridgestone's famous Multicell compound offers escape routes for water that are created from the pressure of the tire on ice and snow to prevent hydroplaning and exploit cohesion. The latest generation features tiny bite particles embedded into the tread that serve as millions of small studs benefitting both snow and ice traction. Due to its high tech compound and tread design, I recommend it highly as the tire offers the best snow traction according to our Tire Survey Results.
The ice and wet focused FleX-Ice silica compound found in the Michelin X-Ice Xi2 was engineered to retain more dry road stability, while still offering amazing traction levels in cold weather. Because of this, it purposefully gives up some deep snow traction when compared to the Bridgestone. However, for areas where 4" or more is not normal, such as urban environments, the Xi2 excels in controlling a car at slippery intersections where ice tends to form due to traffic patterns.
Bridgestone Blizzak WS70
Michelin X-Ice Xi2
Naturally, as with all winter / snow tires and especially with all-wheel drive vehicles, tires should be installed on all four corners, not just two. Watch "Why Gamble With Winter Tire Selection When Four of a Kind Always Beats Two Pair?" to see the benefits of installing four winter / snow tires this winter season.